In the field of semiconductor processing, vacuum processing chambers are generally used for etching and chemical vapor deposition (CVD) of materials on substrates by supplying an etching or deposition gas to the vacuum chamber and application of an RF field to the gas to energize the gas into a plasma state. Examples of parallel plate, transformer coupled plasma (TCP.TM.) which is also called inductively coupled plasma (ICP), and electron-cyclotron resonance (ECR) reactors and components thereof are disclosed in commonly owned U.S. Pat. Nos. 4,340,462; 4,948,458; 5,200,232 and 5,820,723. Because of the corrosive nature of the plasma environment in such reactors and the requirement for minimizing particle and/or heavy metal contamination, it is highly desirable for the components of such equipment to exhibit high corrosion resistance.
In order to protect the chamber walls, U.S. Pat. Nos. 5,366,585; 5,556,501; 5,637,237; 5,788,799; 5,798,016; and 5,885,356 propose liner arrangements. For instance, the '585 patent discloses a free standing ceramic liner having a thickness of at least 0.005 inches and machined from solid alumina. The '585 patent also mentions use of ceramic layers which are deposited without consuming the underlying aluminum can be provided by flame sprayed or plasma sprayed aluminum oxide. The '501 patent discloses a process-compatible liner of polymer or quartz or ceramic. The '237 patent discloses a heater arrangement for heating a metallic liner to a temperature of 100 to 600.degree. C. to impede formation of films on the liner wall. The '799 patent discloses a temperature controlled ceramic liner having a resistance heater embedded therein and the ceramic can be alumina, silica, titania, zirconia, silicon carbide, titanium carbide, zirconium carbide, aluminum nitride, boron nitride, silicon nitride and titanium nitride. The '016 patent discloses a liner of ceramics, aluminum, steel and/or quartz with aluminum being preferred for its ease of machinability and having a coating of aluminum oxide, Sc.sub.2 O.sub.3 or Y.sub.2 O.sub.3, with Al.sub.2 O.sub.3 being preferred for coating aluminum to provide protection of the aluminum from plasma. The '356 patent discloses a ceramic liner of alumina and a ceramic shield of aluminum nitride for the wafer pedestal for use in CVD chambers. U.S. Pat. No. 5,904,778 discloses a SiC CVD coating on free standing SiC for use as a chamber wall, chamber roof, or collar around the wafer. U.S. Pat. No. 5,292,399 discloses a SiC ring surrounding a wafer pedestal. A technique for preparing sintered SiC is disclosed in U.S. Pat. No. 5,182,059.
Prior art attempts at temperature control of liners in plasma processing reactors include arrangements wherein heaters are embedded in the liners or heaters are arranged to thermally conduct heat into the liners. Such arrangements, however, may not provide uniform heating of the liners which can lead to non-uniform processing of individual substrates or process drift during sequential processing of a batch of substrates. As such, there is a need for liner heating arrangements which provide better temperature control of the liner.